Recent Progress of Highly Efficient Red and Near‐Infrared Thermally Activated Delayed Fluorescent Emitters

TLDR

Since the demonstration of high efficiency in pure organic TADF emitters, organic emitters have been widely developed, with most focus on green and blue, but recent studies are increasingly targeting red and near‑infrared emitters for applications in bioimaging, sensors, telecommunications, and night vision. This review examines recent progress in red and near‑infrared TADF emitters to elucidate molecular design principles and structure–property relationships, and proposes future prospects. The authors survey literature on molecular structure–photophysical characteristics and device performance to map structure–property relationships. Although the external quantum efficiency of red and near‑infrared TADF OLEDs is low, it has advanced to close to 30 % for red OLEDs and to the 10 % level for near‑infrared OLEDs.

Abstract

Abstract Organic emitters have been widely developed since the demonstration of high efficiency in pure organic emitters represented by thermally activated delayed fluorescent (TADF) emitters. Pure organic‐based TADF emitters are found to harvest all singlet and triplet excitons for radiative transition processes, like phosphorescent emitters that utilize all generated excitons for light emission by strong spin–orbit coupling. Red, green, and blue organic emitters are investigated, but major interest is focused on green and blue organic emitters. However, recent studies are being directed to red and even near‐infrared emitters because of their wide applications in bioimaging, sensors, telecommunications, and night vision. Although the external quantum efficiency of the red and near‐infrared TADF organic light‐emitting diodes (OLEDs) is low, the external quantum efficiency of red OLEDs has been advanced to close to 30% and that of near‐infrared OLEDs to the 10% level. Therefore, more attention is being paid to red and near‐infrared TADF emitters. In this work, recent progress of the red and near‐infrared TADF emitters is reviewed to understand the molecular design principle and the molecular structure–photophysical characteristics and molecular structure–device performance relationships. In addition, future prospect of the red and near‐infrared TADF emitters is proposed.